Known in the art are various processes for the preparation of allyl chloride.
Thus, known is a process for preparing allyl chloride by thermal gas-phase chlorination of propylene by means of gaseous chlorine at a temperature ranging from 500.degree. to 510.degree. C. The process is carried out in a hollow or partitioned cylindrical apparatus by mixing propylene heated to a temperature of from 340.degree. to 360.degree. C. with cold evaporated high-concentration chlorine with a 6-fold excess of propylene. The reaction product effluent from the reactor is subjected to an abrupt cooling-quenching to inhibit undesirable secondary processes, and is then separated in condensation-stripping columns sprayed by liquid propylene (cf. L. Oshin "Manufacture of Synthetic Glycerol", Moscow, "Khimija" Publishing House, 1974).
Main disadvantages of the above-described prior art process reside in a low yield of allyl chloride and a low conversion of the starting feed equal to 17.8%, a high recycle ratio of propylene (thus, out of 6 volumes of propylene supplied for the reaction 5 volumes are recycled) thus resulting in increased power consumption and losses of propylene. Furthermore, disadvantages of the process are limited product output from a unit working space of the reactor, low capacity of the apparatus, non-efficient utilization of rather expensive chlorine half of which is consumed for the formation of hydrogen chloride.
Also known in the art is a process for preparing allyl chloride by way of oxidizing chlorination of propylene with hydrogen chloride in the presence of air oxygen (cf. U.S. Pat. No. 2,966,515). The starting mixture is passed at a temperature ranging from 300.degree. to 500.degree. C. through a stationary catalyst bed i.e. lithium chloride supported on pumice; the contact time being equal to 0.5-12 sec. The components are taken in the ratio of 1:1:2.5 (propylene:hydrogen chloride:oxygen or air respectively). 90 mol. % of allyl chloride is present in the condensed reaction products.
Also known in the art is a process for preparing allyl chloride by oxidizing chlorination of propylene by means of hydrogen chloride and air oxygen in the presence of catalysts consisting of a mixture of chlorides of different metals (zinc, palladium, copper, potassium, lithium, magnesium, barium, iron, calcium).
The process of oxidizing chlorination is conducted mainly in tubular reactors with a stationary or fluidized bed of catalyst at a temperature within a wide range of from 50.degree. to 500.degree. C. The catalyst is used in the form of granules manufactured from mixtures of different chlorides and in the form of carrier-supported chlorides (pumice, silica gel and the like materials are used as the carrier; cf. USSR Inventor's Certificate No. 363680 published in 1972).
The process according to said USSR Inventor's Certificate is carried out in a reactor with a fluidized bed of a finely divided catalyst consisting, for example, of a mixture of chlorides of palladium, copper, zinc and potassium taken in the molar ratio of 0.1:1:1:1 respectively, deposited onto a carrier, i.e. silica gel. The weight content of palladium in the catalyst should be obligatorily within the limits of 0.3-0.4%.
The yield of allyl chloride as calculated for the passed propylene is 4 to 6%.
Principal disadvantages of the above-discussed prior art processes are: rapid activity drop of the catalyst due to high volatility of metal chlorides and related low yields of allyl chloride causing additional technological troubles at the stage of recovery of allyl chloride from the contact gas, as well as difficulties associated with temperature control in the fluidized bed.
The closest prior art process most resembling that of the present invention (prototype) is the process for preparing allyl chloride by way of oxidizing chlorination of propylene with hydrogen chloride in the presence of air and a manganese dioxide catalyst incorporated in a leaned manganese ore in an amount of from 26 to 28% by weight (cf. USSR Inventor's Certificate No. 525,655). The oxidizing chlorination process is conducted in a stationary bed of catalyst with the ratio of HCl:C.sub.3 H.sub.6 :air=1:1:8 respectively and at a temperature in the reaction zone varied within the range of from 350.degree. to 450.degree. C.
The yield of alkyl chloride in this process, as calculated for the passed propylene is 28.9 vol.% with a selectivity of 85.3% and conversion of propylene of 34%.
Principal disadvantages of this prior art process are: low yield of allyl chloride and low conversion of propylene; a high degree of dilution of the starting raw materials and the reaction products with air (80% by volume), which hinders isolation of the desired product and restricts the process productivity.
Furthermore, disadvantages of the process also are in inevitable combustion of a portion of propylene to CO.sub.2 in connection with the presence of air oxygen in the reaction zone and difficulties associated with organization of an efficient heat removal and control of temperature inside the stationary bed of the catalyst.